The fountain was first erected in wood and plaster to honor the wedding of Cosimo I Francesco to Joanna of Austria in 1565. Neptune was chosen to adorn it as an allusion to Cosimo's naval achievements. Giambologna had a hand in making the nymphs and satyrs around the basin. *** 'The giant in white marble (from which its nickname, Biancone) represents Neptune, the sea god, surrounded by tritons, sea divinities and satyrs. The Fontana del Nettuno, admired also as a sculpture, depicts a mythological scene that makes a great effect upon the spectator: the giant, in fact, seems to show his power and dominate the piazza coming out of the waters pulled by the force of four horses. The bronze figures on each side reproduce the Fluvial Allegories: the oceanic divinity Doride, her daughter Teti and two sea goddesses flanked by satyrs. Desired by Cosimo I (it has been said, because of his passion for the sea), it was commissioned to Bartolomeo Ammannati and to Giambologna. According to some historical records the figure of Neptune reproduces the face of Cosimo I, but it is not certain. The sculptural group owes its fame to the composite scenography and to the strong material contrast: the white marble of Neptune and the horses and the bronze of the Allegories.' Source: http://english.firenze.net/groups/6/29/artI199102.html